DirectX 12 introduces the next version of Direct3D, the graphics API at the heart of DirectX. Direct3D is one of the most critical pieces of a game or game engine, and we've redesigned it to be faster and more efficient than ever before. Direct3D 12 enables richer scenes, more objects, and full utilization of modern GPU hardware. And it isn’t just for high-end gaming PCs either - Direct3D 12 works across all the Microsoft devices you care about. From phones and tablets, to laptops and desktops, and, of course, Xbox One, Direct3D 12 is the API you've been waiting for.

It's great that DirectX works across "phones and tablets, to laptops and desktops, and, of course, Xbox One", but an important adjective is missing here: Windows. With Microsoft playing little to no role in smartphone and tablets, and the desktop/laptop market being on hold, how much of a plus is DirectX on phones and tablets, really? Doesn't Windows Phone's and Windows 8 Metro's reliance on it only make it harder for game developers and houses to port their iOS and Android games over?

In what way it stifles innovation? As andrewclunn points out just above, OpenGL is the one playing catch up trying to copy what DirectX pioneers.

Lock-in stifles innovation, because it removes the competition factor, since you end up with a monopoly. Fighting to get people locked in doesn't stifle it, because you're competing to get folks to come to your platform in the first place.

The core problem really is that using DirectX ties you to Windows, which almost inevitably leads to your software becoming Windows-specific in a lot of other ways. So, porting to something other than DirectX can be a pain, and you can't distribute your software on other platforms.

Too often, the folks on the Linux side have similar issues, because Windows lacks a lot of stuff which exists on pretty much every *nix system on the planet (and thus almost everything other than Windows). So, it's not just a Windows problem. But those issues can be (and sometimes are) fixed by porting various libraries to Windows, whereas Microsoft isn't about to port DirectX to Linux or any other OS.